The present invention relates generally to implantable medical devices and more particularly to implantable medical devices intended for use in monitoring a patient""s heart rhythm or other physiologic parameters.
Implantable pacemakers and cardioverters monitor the heart""s rhythm in order to detect arrhythmias and deliver appropriate therapies to terminate detected arrhythmias. In conjunction with this function, the ability of the device to store information with regard to monitored heart rhythms has dramatically increased over the past two years. Examples of implantable pacemakers and defibrillators which have the capability of storing information related to monitored heart rhythms include U.S. Pat. No. 4,223,678 issued to Langer et al., U.S. Pat. No. 5,722,999 issued to Snell, U.S. Pat. No. 5,513,645 issued to Jacobsen et al. and U.S. Pat. No. 5,312,446 issued to Holschbach et al. In addition, there have recently been developed implantable monitoring devices that do not deliver any anti-arrhythmia therapies to the heart but simply store information regarding a patient""s heart rhythms for later uplink to an external device. Such devices are disclosed in U.S. Pat. No. 5,331,966 issued to Bennett et al., U.S. Pat. No. 5,135,004 issued to Adams and U.S. Pat. No. 5,497,780 issued to Zehender.
In conjunction with implantable devices as described above, information stored relating to a patient""s heart rhythm may include information relating to heart rate trends over time, as disclosed in U.S. Pat. No. 5,088,488 issued to Markowitz et al., U.S. Pat. No. 5,330,513 issued to Nichols et al. and U.S. Pat. No. 5,603,331 issued to Heemels et al. as well as information relating to heart rate variability over time, as disclosed in U.S. Pat. No. 5,749,900 issued to Schroeppel et al., U.S. Pat. No. 5,466,245 issued to Spinelli et al., U.S. Pat. No. 5,411,131 issued to Yomtov et al. and U.S. Pat. No. 5,437,285 issued to Verrier et al. Other information relating to heart rhythms may also be stored, particularly in conjunction with occurrences of cardiac arrhythmias. Storage of such information, along with information relating to the patient""s condition or treatment is disclosed in U.S. Pat. No. 4,561,442, issued to Vollmann, U.S. Pat. No. 5,722,999, issued to Snell and U.S. Pat. No. 4,295,474, issued to Fischell, all incorporated herein by reference in their entireties.
In addition to storing information relating to heart rhythms, implantable devices may also store information regarding outputs of physiologic sensors such as activity sensors, respiration sensors and the like. For example, storage of sensor output trends is disclosed in U.S. Pat. No. 5,088,488 by Ledin et al. Storage of long term trends of heart rates and activity sensor or other physiologic sensor output is disclosed in the above-cited commonly assigned U.S. patent application Ser. No. 09/078,221, filed May 13, 1998 by Stone et al., for an xe2x80x9cImplantable Medical Device for Tracking Patient Functional Statusxe2x80x9d, U.S. patent application Ser. No. 09/452,659, filed Dec. 1, 1998 by Padmanabhan et al., for a xe2x80x9cMethod and Apparatus for Monitoring Heart Ratexe2x80x9d and U.S. patent application Ser. No. 09/452,452,533, filed Dec. 1, 1999 by Padmanabhan et al., for a xe2x80x9cMethod and Apparatus for Monitoring Heart Ratexe2x80x9d, both incorporated herein by reference in their entireties
The present invention is directed toward an implantable device having enhanced capabilities for monitoring a patient""s condition and/or the patient""s response to therapies provided by the implanted device over extended periods of time, e.g. time periods of over a months, preferably time periods extending over several months. The implanted device, in conjunction with an associated external monitor or programmer provides a mechanism displaying these monitored parameters in conjunction with simultaneous time-based display of significant events associated with an ongoing treatment regimen. Preferably, monitored physiologic parameters and information indicative of the patient""s response to delivered therapies are displayed in the form of trend lines, histograms or scatter plots illustrating values of the measured parameters on one axis and time on another axis. Multiple physiologic parameters are preferably simultaneously displayed on the same time scale. Events associated with an ongoing treatment regimen are simultaneously displayed, arranged along a time axis corresponding to the time axes of the displayed physiologic parameter trend lines. Displayed events preferably include significant occurrences associated with the ongoing therapy, such as initiation of the therapy, termination of therapy, changes in the therapy and other changes in the patient""s condition or lifestyle. By displaying the monitored parameters in concurrent with and along the same time scale as the significant therapeutic events, the effectiveness of therapies delivered by the device and/or by the patient""s physician over time may be determined and adjustments to the therapy may more easily be evaluated.
In the context of a therapy delivered by an implantable pacemaker, for example, the therapies may include anti-bradycardia cardiac pacing, anti-tachycardia cardiac pacing, and tachyarrhythmia prevention cardiac pacing or pacing for treatment of heart failure. In conjunction with such devices, the significant events to be displayed may include initiation of a pacing mode, changes of pacing mode, changes in electrode configurations or changes in pacing parameters within a pacing mode, such as rate response adjustments, lower pacing rates changes, and activation or deactivation of optional features within a pacing mode, such as rate-variable refractory periods or A-V intervals, rate smoothing, or the like. In the context of an implantable anti-tachyarrhythmia device, significant events to be displayed might include delivery of, enablement of or changes in the therapies provided, e.g. anti-tachycardia pacing therapies and high voltage therapies, as well as changes in the detection criteria for triggering the therapies. In the context of an implantable drug dispenser, such events might include initiation of delivery of a drug, changes in the drug delivered and modification of the timing or dosage of the delivered drug. Correspondingly, changes in the operational parameters of implantable nerve or muscle stimulators, implantable apnea stimulators or the like may also be monitored.
Physiologic parameters to be monitored may include the types of parameters presently monitored by implantable devices such as pacemakers, defibrillators, implanted monitors and the like, such as heart rate, heart rate variability, patient activity levels, hemodynamic parameters, respiration, blood oxygen levels, ST segment elevation or depression, occurrences of tacharrhythmias, QRS or ST segment morphology and the like. In conjunction with the display of detected tachyarrhythmias, information relating to the rates of the detected tachyarrhythmias and/or the detection criteria then in effect for the tachyarrhythmias may also be displayed. As implanted chemical sensors are further refined, for example in conjunction with implantable drug pumps, monitored parameters may include blood glucose level, electrolyte levels, metabolite levels or other chemical parameters of diagnostic interest with respect to the drug regimen provided by the device. Monitored parameters indicative of the effect of the therapy provided by the implanted device may include numbers and timing of delivered therapies and effectiveness of delivered therapies. Similar parameters to those discussed above may also be monitored by implanted monitoring devices which themselves do not deliver a therapy, and may also be displayed along with significant events associated with therapies provided by other means, such as orally delivered drug regimens, dietary regimens, surgical procedures or the like.
In some embodiments of the invention, all information to be displayed, including the monitored parameters and the therapy related events are stored in the implantable device. In other embodiments, the displayed information may be stored partly in the implantable device and partly in conjunction with an external programmer or monitor. In still other embodiments, all displayed information may be permanently stored in the external programmer or monitors. In embodiments of all three types, it is envisioned that in general, at least some physiologic parameters to be displayed are acquired by the implantable device and transmitted by telemetry to the associated external programmer or monitor. Display of the information may be accomplished by means of a CRT or LCD type display and/or by means of a paper print-out.